The present invention relates to portable temperature sensing surface probes and more particularly concerns a probe of improved reliability and more rugged construction.
Portable temperature probes are used for sensing temperature in many different applications and are made of many different configurations. Commonly, such probes use platinum resistance temperature detectors (RTD's) or thermocouples and are made, in general, for immersion or for surface contact. The surface contacting probes employing platinum resistance frequently have the sensing element encased within an enclosed body of high heat conductivity and thus provides some measure of protection for the delicate sensor resistor. Such complete protective enclosures are not available with a thermocouple sensor in which the thermocouple junction must be placed in direct contact with a surface to be measured. If direct contact between the thermocouple junction and the surface to be measured is prevented, as by complete enclosure of the junction, the loss is thermal sensitivity may be so great as to be unacceptable in many precision applications. In U.S. Pat. No. 3,834,237 to Robertson a thermocouple surface temperature probe is shown which employs a metal shield surrounding the thermocouple wires, the shield being open at its surface contacting end to permit exposure of the thermocouple junction. In such an arrangement the thermocouple junction projects outwardly of the thermocouple probe body and outwardly of the protective shield and thus is subject to undesired or inadvertent impact or abrasion which can seriously damage the thermocouple junction or its mounting structure. Attempts to place the protective shield close enough to the junction in order to provide adequate physical protection adversely affect the precision temperature sensing and may require supplementary heater sections to heat the shield, as described in the Roberts patent.
Accordingly, it is an object of the present invention to provide a surface temperature probe that minimizes or avoids above-mentioned problems.